The present invention relates to a valve, particularly for pressure exchanger installations comprising pressure exchangers with tubular chambers through which an alternating flow takes place, a rotatable closing element arranged inside a housing, the housing having a plurality of connections for connecting lines, the housing being connected to a first pipe system and in each case one end of at least one pressure exchanger, a respective other end of each pressure exchanger being connected through a valve to a second pipe system, and the closing element being provided with a motor-operated drive shaft.
In order to treat water, the reverse osmosis process is often used. In this process, a fluid stream to be purified is forced at high pressure through a membrane system which, in the case of large quantities of fluid, comprises a plurality of membrane modules. In such membrane modules, separation into pure water and an enriched concentrate is carried out through a membrane, since only some of a fluid to be purified can flow through a membrane. The proportion flowing through emerges as a usable proportion, as pure water or else permeate, on the other side of the membrane. The part which does not flow through leaves a membrane module as brine, a concentrate of the fluid enriched with salts and minerals, as a proportion which cannot be used and is under high pressure. This pressure is around 2 bar with a module inlet pressure of about 65 bar.
U.S. Pat. No. 5,306,428 discloses a reverse osmosis installation in which pressure exchangers in the form of tubular chambers are used to recover energy. By using these, the still high pressure of the high energy brine flowing out of the membrane module is transferred to a fluid still to be purified. Thus, a pump drive output which is lower by the amount of this pressure increase is required for the fluid to be introduced in order to generate the high pressure needed for the reverse osmosis process.
In order to control and/or switch the fluid paths of the brine into and out of the pressure exchangers, a Valve with a rotating closing element is used, in addition to other Valves. By using such a Valve, the tubular chambers of the pressure exchangers have brine emerging from the membrane modules applied to them alternately. The rotating closing element is constructed as a roll, in which connecting ducts are arranged in the manner of a three-way valve. During the changeover operations, all the flow paths are shut off completely. In order to avoid pressure surges during such changeover operations, pressure equalizing ducts are arranged within the roll.
Depending on the operating period of a membrane, its separation capability decreases and a fluid to be purified has to remain for a correspondingly longer time within a membrane module. For this reason, in the prior art, the changeover times of the roll are regulated using an actuating motor. However, this valve is suitable only for small reverse osmosis installations, since the flow cross sections within the valve are approximately the same size as the flow cross sections of the ducts to be filled. In large installations and the fluid columns to be displaced therein, and as a result of the forces necessitated thereby, a considerable problem of dimensioning the valve arises.